DESCRIPTION: The long-term objective of this proposal is to expose basic molecular mechanism by which ion channels operate. Potassium channels transfer K+ ions across membranes and in this capacity they are central to the function of all cells, not only muscles and nerves. The structural bases for the function and dysfunction of these critical membrane proteins are only now being uncovered. Recent advances in molecular biology and high-resolution techniques for studying channels have combined to kindle an explosion of new information about how structure, mediates function. The minimal K+ channel (minK) is uniquely suited for this type of analysis. As its name suggests, it is the smallest eukaryotic channel protein known. Despite its apparent simplicity, the channel is voltage-gated, K+-selective and tightly-regulated. Indeed, minK appears critical to both cardiac and auditory electrical activity. This project has four specific aims that attempt to uncover basic structural elements of minK function through study of the residues that line its conduction pore, the sites that mediate open-channel blockade and the channel's subunit composition. The minimal K+ channel merits this type of investigation because of its role in mammalian physiology and its potential to reveal important principles of channel function through its structural simplicity.